Ultimate Guide for oligonucleotide therapeutics

What’s oligonucleotide therapeutics

Oligonucleotide Therapeutics is an innovative drug therapy that acts on human DNA/RNA. It achieves therapeutic effects by modifying genes, completing some gene fragments, and covering and masking problematic gene fragments. Usually, it requires regular injections or other forms of medication intake, such as one injection per year, or through gene modification to achieve a permanent solution. This type of oligonucleotide drug is commonly used in the treatment of some rare diseases, such as cardiovascular diseases and AIDS.

Definition of Oligonucleotide Therapeutics

Oligo Therapeutics refers to a type of precise drugs that utilize artificially synthesized short-chain nucleic acids (DNA or RNA), which precisely pair with the target genetic material within the body, thereby blocking or regulating the production of pathogenic proteins at the genetic level.

Difference between oligo drugs and small molecure drugs

The most significant difference between it and traditional drugs (small molecule drugs or protein drugs) lies in that it directly acts on genetic material (RNA or DNA), intercepting diseases from the “source”.

Mechanism of Action

Traditional small molecule drugs exert therapeutic effects by physically binding to target proteins. It is currently known that only approximately 15% of human proteins can effectively bind with small molecule drugs, while the remaining approximately 85% of proteins are difficult to target in this way. This is one of the main reasons why the range of diseases that small molecule drugs can treat is relatively limited.

Drug Metabolism

Small molecule drugs typically have a relatively low molecular weight (< 500 Da) and can penetrate cell membranes, thus they are mostly administered orally. However, due to their easy metabolism and clearance by the body, they often require long-term or frequent dosing. In contrast, oligonucleotide (OLIGO) drugs have a larger molecular weight and often carry a strong negative charge, making it difficult for them to penetrate cell membranes on their own. Therefore, they are usually administered via subcutaneous or intravenous injection. These drugs have a long-lasting effect, and the effect of a single dose may last for several months or even half a year or more. Some RNA drugs can exert their effects by influencing gene expression, and theoretically, they have the potential to achieve long-term or even permanent therapeutic effects.

Research and Development and GMP Production

The research and development of small molecule drugs requires finding compounds that can precisely bind to specific proteins, a process that is extremely difficult. In the early stages of research and development, it is usually necessary to screen tens of thousands of candidate molecules, and it is easy to fail in the preclinical stage due to toxicological issues. Therefore, it usually takes more than ten years for a small molecule drug to go from research and development to market. However, oligonucleotide (OLIGO) drugs can be designed based on the gene sequence of the target, and multiple candidate drugs can be obtained within a few days. For example, the customized drug Milasen for a single patient, from genetic testing to obtaining FDA clinical trial approval (IND), only took 10 months.

Difficulty of FDA Approval

Small molecule drugs:

Strict standards, intense competition in the global market. And the reality is that the current small molecule drugs have been developed with all kinds of drugs already cover all disease that can cure by the small molecule drugs, that means it’s difficult to develp new function of the drugs. Since  the FDA usually requires new drugs to have new functions or specificity that are different from existing similar drugs.FDA has extremely mature and strict standards for the safety, impurity control, and metabolites of small molecules.

Oligo drugs:

Standards are still being refined: As a completely new type of drug, the FDA’s standards for impurity detection, immunogenicity (whether it causes an immune response), and delivery systems (such as LNP toxicity) are still being refined.

Policy benefits: Many Oligo drugs target rare diseases (Rare Diseases) or incurable diseases such as cancer. Out of humanitarianism, when patients are facing life-threatening situations and have no other treatment options, the FDA has a special approval channel for such drugs. The FDA often grants “Orphan Drug Designation”, “Breakthrough Therapy”, or “Accelerated Approval”. For example, as long as it is proven that the drug can significantly reduce the indicators of a certain pathogenic protein, it can be marketed without a long-term survival observation.

Major Types of Oligonucleotide Therapeutics and  how they Work Inside the Human Body

How does oligonucleotide enter the human cell

Step 1: Blood flow and cell contact: Oligo drugs are first administered into the human body via intravenous injection or subcutaneous injection. Once in the bloodstream, ASO drugs, with their good structure and stability, can typically come into contact with the cell membrane. However, siRNA drugs need to be delivered into cells in combination with delivery systems such as Galnac or LNP.

Step 2: Cell phagocytosis: The cell membrane invaginates inward to enclose the oligo drugs, forming an endosome. 99% of the oligo drugs are degraded by the endosome and expelled, while approximately 1% of the oligo drugs penetrate the endosome membrane before degradation and are released into the cytoplasm.

Step 3: Entering the cytoplasm or nucleus: After successfully escaping from the endosome, oligo drugs enter different regions based on their functions. siRNA drugs enter the cytoplasm, while ASO drugs can enter either the nucleus or the cytoplasm.

Step 4: Exerting therapeutic effects: Different oligo drugs have distinct mechanisms of action.

Antisense Oligonucleotides (ASOs)

ASO (antisense oligonucleotide, usually a single strand of DNA or modified nucleotides) binds to the target mRNA (located in the cytoplasm or nucleus), forming a DNA-RNA or RNA-RNA hybrid chain. Different types are designed based on the chemical structure of Based on different structures of ASO:

1. The structure of ASO is Gapmer (DNA in the middle and modified RNA at both ends), that is, a DNA-RNA hybrid chain. This hybrid chain attracts RNase H1 in the cytoplasm or nucleus, while RNA-RNA does not. RNase H recognizes and cuts the mRNA in the hybrid chain, preventing it from being translated into protein, thereby achieving gene silencing.
2. The structure of ASO is fully modified, for example, all nucleotides are modified with 2′-MOE, LNA or morpholino oligomer PMO. This ASO forms an RNA-RNA double-stranded structure with pre-mRNA. They recognize specific signal sequences on pre-mRNA and cover them. When the splicing machinery (small nuclear ribonucleoproteins, snRNPs) comes to search for splicing sites, it is blocked and cannot interact with the sequence of pre-mRNA. This leads to exon skipping or intron retention, generating new protein variants or repairing damaged proteins. This is also one of the most successful application fields of ASO at present.

siRNA Oligonucleotide Therapeutics

siRNA is a double-stranded structure, and its mechanism of action mainly occurs in the cytoplasm. After escaping from the endosome, siRNA will be recognized and captured by a protein complex called RISC (RNA-induced silencing complex). Inside RISC, the double strands of siRNA will be unwound. One of the strands is discarded, while the other carries the guide strand and the RISC complex in the cytoplasm recognizes the target mRNA and binds to it. The core protein Argonaute 2 (Ago2) in the RISC complex will cut the target mRNA at a specific location. The cut mRNA becomes extremely unstable and is then completely degraded by the intracellular exonucleases within the cell, thereby preventing protein synthesis.

Crisper gRNA drugs

The crisper gRNA is usually composed of two parts. The crRNA (containing a sequence of approximately 20 nucleotides) binds to the target DNA through base complementary pairing, while the tracrRNA tightly fixes the gRNA onto the Cas9 protein. After the gRNA binds to the Cas9 protein, it searches for the specific DNA sequence of the target in the cell. The Cas9 protein first looks for the specific short sequence of the PAM (protospacer adjacent motif) near the target DNA. Once the PAM is found, the crRNA part of the gRNA will “zipper-like” pair with the target DNA strand. Once the pairing is successful, the Cas9 protein will cut the DNA double strand at a specific location, causing a double-strand break (DSB). 

After the DNA is cut, the cell will activate its self-repair mechanism:

Gene knockout: If the repair is incorrect (non-homologous end joining), the gene will be inactivated.

Gene knock-in: If a template DNA is artificially provided, the cell can precisely repair and insert the new gene sequence according to the template.

miRNA and anti-miR Therapies

MicroRNA (miRNA) is a type of short non-coding RNA naturally produced within cells. It achieves the purpose of preventing mRNA translation or inducing its degradation by binding to mRNA. After entering the cytoplasm, miRNA is loaded into a protein complex called RISC (RNA-induced silencing complex). Unlike ASO and SIRNA, which precisely target specific gene fragments, miRNA matches gene sequences in a broad and fuzzy manner. This is because diseases like cancer or Alzheimer’s often involve not just one gene but an entire signaling pathway going awry. A single miRNA mimic can simultaneously suppress 10 to 100 mRNAs on the same pathway. However, the downside is that it can easily mis-target normal mRNA fragments, leading to off-target effects. Therefore, miRNA is currently mostly in the clinical stage.

Anti-miR (also known as antagomirs) are artificially synthesized oligonucleotides. There are thousands of miRNA sequences in the human body, and anti-miR is designed to inhibit those pathogenic miRNAs that are overexpressed. Once Anti-miR binds to miRNA, the miRNA can no longer bind to the target mRNA, allowing the previously suppressed genes to resume expression.

Aptamers Oligonucleotide Therapeutics

Aptamers are short chains composed of dozens of nucleotides (DNA or RNA). However, unlike ASO and siRNA, which bind to target mRNA through base complementarity, aptamers are similar to antibodies and mainly function extracellularly, on the cell membrane surface, or intracellularly. Their three-dimensional-like structures can complementarily match the shape of target molecules and bind to target proteins with high affinity through van der Waals forces, hydrogen bonds, and electrostatic interactions. Their binding targets include proteins, receptors, enzymes, and small molecules (such as ATP, VEGF, etc.). When entering cells or circulating in the blood, aptamers bind to the active sites of pathogenic proteins, preventing the proteins from binding to their natural ligands. They can also induce beneficial signal transduction by binding to and activating certain cell surface receptors. Additionally, many aptamers are designed to recognize specific receptors on the surface of cancer cells, and upon binding, trigger “receptor-mediated endocytosis” to precisely deliver attached chemotherapy drugs or siRNA into the cells.

Some FDA Approved Oligonucleotide Therapeutics

Following table highlights the evolution of oligonucleotide therapeutics from a niche “orphan drug” category into a mainstream pharmaceutical powerhouse. Since the landmark approval of the first ASO in 1998, the field has expanded through the clinical breakthrough of siRNA in 2018 and the specialized application of Aptamers in ophthalmology. These drugs leverage precise molecular recognition—whether through genetic base-pairing or 3D structural folding—to hit “undruggable” targets that traditional small molecules and antibodies cannot reach, effectively ushering in the “third wave” of modern medicine.

Note: This list includes representative FDA-approved oligonucleotide therapeutics. Information is updated as of early 2026.

Why Oligonucleotide Therapeutics Are the Next Generation Drugs

Breaking Through Disease Limitations

Traditional small molecule drugs act directly on proteins. However, about 80% of the pathogenic proteins in the human body have smooth surfaces, and traditional drugs cannot bind to them. Small nucleic acid drugs act on intermediates (mRNA) or directly on DNA. As long as there is a specific gene sequence, theoretically any disease can be designed with corresponding specific drugs.

Precision Medical Treatment

Oligonucleotide drugs enter the bloodstream through a delivery system such as GalNAc. After the drugs enter the bloodstream, the vast majority of them will directly enter the liver and not enter other tissues. This greatly reduces systemic side effects and concentrates the drug effect at the lesion site.

Shorter Development Cycle

The development period for small molecule drugs usually takes 10–14 years, while oligonucleotide drugs is shortened to 7–10 years. Oligo drugs can be designed based on computer analysis of the genetic sequence. Once a sequence is designed, its chemical properties (such as solubility and stability) are highly similar to those of similar drugs.

Long-Lasting Efficacy

Traditional small molecule drugs require long-term medication use because they work by binding to already existing proteins (such as enzymes and receptors). However, cells are constantly producing new pathogenic proteins. In contrast, oligonucleotide drugs have a long half-life within cells and can be recycled (for example, one siRNA can cleave multiple mRNAs). Many drugs have achieved the ability to be injected only once every six months or even once a year (such as the lipid-lowering drug Inclisiran). Drugs like CRISPR gRNA can achieve lifelong immunity through acting on DNA, even with a single treatment.

Nucleic acid drugs synthesis process and facilities required for oligonucleotide therapeutics

Two types of modern approaches to therapeutic oligonucleotide manufacturing

There are two main methods for the production of therapeutic oligonucleotides in modern times , they are chemical synthesizing (Solid-Phase Chemical Synthesis) and enzymatic/biocatalytic synthesizing. Chemical synthesis involves the stepwise addition of nucleotide units on a solid-phase support, such as CPG (Controlled Pore Glass), to synthesize oligonucleotides of a specific sequence.

Solid Support Synthesis Method

There are two mainstream approaches to chemical synthesis: 

• Resin synthesis method
• CPG synthesis method

Enzyme-catalyzed synthesis

Enzyme-catalyzed synthesis method is using biological enzymes such as DNA or RNA polymerase, transcribing enzyme, etc., under the guidance of a template, specific sequences of nucleic acids are synthesized. It is mainly used for the synthesis of long-chain oligonucleotides or mRNA (over several hundred to several thousand nt). Enzyme catalysis requires strict temperature control, buffering, and enzyme activity maintenance. The cost of enzyme-catalyzed synthesis is usually higher than that of solid-phase carrier (Resin/CPG) chemical synthesis. Moreover, the products generated by enzyme catalysis often contain a large amount of short-chain deletions or impurities, and more complex purification methods (HPLC, PAGE, etc.) are required. For medium-length oligos (several tens to several hundred nt), the efficiency of enzyme catalysis is low, and the yield decreases. Therefore, in the oligonucleotide field, solid-phase synthesis is still the current mainstream method.

The main process of oligo synthesizing using solid support method

Solid-phase chemical synthesis, also known as the phosphoramidite solid-phase synthesis method, in general, is the process of covalently fixing the starting nucleotide onto a high-porosity solid support (such as CPG or resin support), and through repeated cycles of deprotection, coupling, sealing and oxidation in a heterogeneous system, achieve the directional extension of nucleotide monomers from the 3′ end to the 5′ end.

The core cycle process of solid-phase chemical synthesis

Step 1 De-blocking: Using acidic reagents (such as TCA/DCM), the 5′ carbon atom of the 5′-position of the ribose (or deoxyribose) sugar ring of the terminal nucleotide is removed, thereby removing the DMT (4,4′-Dimethoxytrytyl) group protecting the 5′-position, exposing the nucleophilic hydroxyl group -CH2-OH.

Step 2 Coupling (Linkage): Activated nucleotide monomers (typically phosphoramidite derivatives) react with the 5′-hydroxyl groups exposed on the solid-phase carrier under the action of a catalyst, forming stable phosphodiester bonds, thereby extending the oligonucleotide chain.

Step 3 Capping: To reduce the accumulation of missing sequences, strong acylation agents such as acetic anhydride are used to cap the 5′-OH groups that are not involved in the coupling reaction, thereby inactivating them in subsequent cycles.

Step 4 Oxidation: By introducing an iodine solution, the unstable trivalent phosphorus is oxidized to pentavalent phosphorus, thereby forming a stable phosphate diester bond framework.

Step 5 Cycling: The elongation process involves a recurring cycle of deprotection, coupling, capping, and oxidation, continuing until the desired oligonucleotide sequence is complete.

Step 6 Detachment: from the carrier (Cleavage): After the synthesis is completed, the oligonucleotides are still attached to the solid-phase carrier, and the bases still carry protective groups that prevent chemical reactions. Chemical reagents such as concentrated ammonia water (NH_4OH) or methylamine ($CH_3NH_2$) or AMA are used to cut the synthesized oligonucleotides off the carrier. Using AMA results in a rapid reaction, and they can be removed from the carrier within 20 minutes typically.

Step 7 Deprotection of Bases: Removal of the protecting groups (such as benzyl, acetyl, etc.) attached to the nucleotide bases, resulting in a fully functional oligonucleotide. At this point, the FLP product has been obtained.

The role of solid support in oligonucleotide therapeutics

Solid support serves as the foundation framework for synthesizing oligos. For instance, controlled pore glass (which typically consists of glass beads or polymer particles with diameters of several tens of micrometers) provides a fixed point for the synthesis chain. It can covalently attach the first base of the nucleotide sequence to the carrier through a chemical bond (usually a succinate ester bond), ensuring that the synthesis reaction proceeds strictly in the 3′ → 5′ direction and adds bases one by one.

PS resin is a tightly interwoven *dense sponge composed of polymer chains. Nucleotide synthesis occurs on the functional groups of thousands of polymer chains within the resin particles. When solvents such as acetonitrile (ACN) are added, these polymer chains will absorb the solvents and expand, causing the originally compact “sponge” to expand. After the resin swells, it forms a form similar to gel-like. At this time, the nucleotide monomers in the solvent can pass through the gaps and enter the interior of the resin balls to search for attachment points. In the same volume, the reaction sites provided by the resin are far more than those of CPG, even tens of times more.

The carrier, such as CPG, is filled with numerous tiny holes (ideally in a cylindrical shape), which protect the growing nucleotide chains and prevent them from tangling with each other. By controlling the pore size and surface chemical activity of CPG, the amount of product that can be synthesized per gram of support can be precisely controlled.

Why resin support not suitable for long chian bases synthesizing

In the three-dimensional space of the resin, long-chain molecules are very prone to interweaving with each other. Moreover, as the synthesized chains become longer, negatively charged DNA/RNA chains accumulate more and more within the resin. These long chains occupy a large amount of space within the resin, causing it to become increasingly “crowded” and “viscous” (Pore Exclusion). As the chains grow, the swollen polymer network becomes like thick glue.
Therefore, the large monomer molecules find it increasingly difficult to diffuse into the center of the resin beads. In the long-chain synthesis process, even a 1% decrease in efficiency, after 100 cycles, the final yield will approach zero.

Current Challenges in Oligonucleotide Synthesis (60nt+)

The transition from laboratory-scale research to commercial GMP manufacturing for long-chain oligos (like Aptamers or gRNA) faces four critical technical and economic bottlenecks:

1. The Synthesis Deadlock: Length vs. Output

The industry struggles with an inability to achieve high-output long-chain synthesis.

• Resin Suitability: While Polystyrene (PS) resin offers high loading, it is generally unsuitable for sequences over 50–60nt due to increased steric hindrance within the gel-like matrix.
• The CPG Trade-off: Using large-pore CPG (e.g., 2000Å) to accommodate long chains results in ultra-low loading capacities. This leads to incredibly low A260 OD values, making it economically unviable for industrial-scale production.

2. Low Crude FLP (Full-Length Product) Purity

For sequences exceeding 60–100 nucleotides, the crude FLP purity typically drops below 30%–60%. This creates a complex “impurity soup” containing truncated sequences and chemically modified by-products, presenting a massive quality control burden.

3. Scale-up Consistency and GMP Production (60nt+)

Scaling up to GMP standards for long-chain oligos is plagued by unpredictable batch-to-batch variation.

• The Yield Crisis: The root cause is the low loading capacity of CPG, resulting in diminished total yield and FLP output, as resin supports are not viable for these lengths.
• Mass Transfer & Consistency: Ensuring uniform reagent penetration at a multi-mol scale is difficult, leading to volatile yields that pose significant compliance risks.

4. Massive Bottlenecks in Downstream Processing (DSP)

Upstream inefficiencies directly cripple purification. Because the starting material for long-mers is of such low quality, the “Downstream” becomes the most expensive part of the facility:

• Complex Impurity Removal: Purification must filter out truncated N-x sequences, residual DMT groups, AMA/ammonium residues, and numerous “unknown” impurities with undefined molecular weights.
• Infrastructure & Analysis Cost: Analyzing these unknown components and executing the multi-stage purification steps require a massive investment. A single oligo synthesis line often requires an entire dedicated building for purification facilities to handle the volume and complexity.
• Massive Recovery Loss: To reach the 95%+ purity required for clinical use, a significant portion of the “good” product is lost during the purification “cut,” resulting in an astronomical Cost of Goods (COGS).

Poresynsolutions’ New Architecture CPG solid support

Unlike traditional functionalized CPG solid support manufacturers, Poresynsolutions‘ technology utilizes the rigid pore structure of CPG as a scaffold, which is then uniformly coated with an ultra-thin (nanometer-scale), permanent Polystyrene (PS) layer. This hybrid design ensures that even at large pore sizes like 2000Å, the structure remains incredibly stable, eliminating the fragility issues common in conventional high-pore glass. To align with the marketing request, poresyn has developed all series of functionalized hyper-link CPGS, like our DNA or RNA modified HL-CPG, 2’OME modified, LNA modified,2′-F modified, reverse HL-CPG, etc. Each of our products had undergo strict quality inspection, we offer COA with critical parameters for customers’ checking before delivery.

The Hybrid Advantage: High Loading Meets Long-Chain Precision

By shifting the chemical reaction from the silica surface to the high-performance PS coating, PoresynSolutions achieves the high-loading capacity of resin while maintaining the defined pore environment necessary for long-chain synthesis.

Key Advantages include:

• Unprecedented Loading Capacity: Achieve 3–6× higher loading than traditional functionalized CPGs, drastically increasing the A260 OD yield per gram.
  • 500Å: 240 μmol/g
  • 1000Å: 180–200 μmol/g
  • 2000Å: 160–180 μmol/g
• Superior Crude Purity: Realize >80% crude oligo purity for long-mers, thanks to the chemical inertness of the coating during both synthesis and downstream treatment.
• Exceptional Durability: High resistance to both acidic and basic conditions, ensuring structural integrity throughout the synthesis cycle.
• Dimensionally Stable: Zero swelling—the material remains stable under all reaction and heating conditions, ensuring consistent flow rates in GMP columns.
• Zero Silica Contamination: Eliminates the risk of silica leaching or “fines,” preventing pipeline clogging and protecting expensive downstream purification equipment.

Oligonucleotide Manufacturing Related Equipment

Modern oligonucleotide production is a specialized engineering feat that scales from high-throughput discovery to GMP-compliant manufacturing. For advanced therapies—particularly long-chain sequences (>60nt)—the equipment must balance chemical precision with industrial volume.

The manufacturing workflow is a high-stakes pipeline: Upstream Synthesizers build the sequence, Reaction Vessels handle the critical cleavage chemistry, and Downstream HPLC/TFF systems perform the heavy lifting of purification. In the era of next-generation medicine, the goal is “Synthesis Efficiency”—using advanced carriers to maximize output while minimizing the massive infrastructure footprint typically required for downstream processing.

Oligo Synthesizer

• Channel Configuration: Common setups include 8 or 12 channels (R&D); 48 or 96 channels (Pilot/Mid-scale); and 120, 192, or 768 channels for high-throughput library and primer production.
• Technical Edge: High-channel systems have very small reaction volumes. While traditional supports yield negligible amounts per well, Poresyn Hybrid Carriers ensure high absolute OD output even in 120+ channel plates.

Synthesis Columns

• Materials: Typically constructed from PEEK, 316L Stainless Steel, or Borosilicate Glass.
• Scale Capacity: Ranges from laboratory scales of 50 nmol to industrial scales of 50 mmol, 1 mol, and beyond.
• Requirement: Must withstand 5–10 bar pressure with frit sizes precisely matched to Poresyn carrier particle distribution to prevent leakage.

Cleavage & Deprotection (C&D) VesselsPost-Processing

• Manufacturer Type: Typically produced by specialized Pressure Vessel Fabricators.
• Core Specs: High-grade corrosion resistance (for concentrated Ammonia/Methylamine) and precise thermal management to prevent long-chain degradation.

Preparative HPLC (Prep-HPLC)

• Function: Isolates the Full-Length Product (FLP) from N-x truncated sequences. Poresyn’s >80% crude purity significantly reduces the operational burden and solvent waste on these systems.

Liquid Chromatography-Mass Spectrometry (LC-MS)

• Role: Essential for verifying the molecular weight of 60nt+ oligos and identifying residual DMT or N-x impurities.
• Price Tiers: Entry-level/Routine: $150k – $300k USD; High-Res Q-TOF/Orbitrap: $500k – $1M+ USD.

Industrial Lyophilizer (Freeze Dryer)

• Purpose: Converts purified liquid oligonucleotides into stable, dehydrated powder for long-term storage.

The Importance of Cell Delivery for Oligonucleotide Therapeutics

Efficient cell delivery is a key factor for the success of oligonucleotide drugs. Unlike antisense oligonucleotides (ASO) that can enter cells without any assistance, small interfering RNA (siRNA) requires a specialized cell delivery system to cross the cell membrane and reach the cytoplasm. Traditionally, FLP (full-length product) oligonucleotides are first synthesized and then coupled with cell delivery groups such as GalNAc. Although this method is effective, the post-synthesis coupling requires additional purification steps, thereby increasing the complexity and cost of the process.

In recent years, advancements in medicinal chemistry have made it possible to directly incorporate cell delivery groups during the synthesis stage. For instance, attaching GalNAc directly to a solid-phase carrier (such as CPG) enables the generation of oligonucleotides with GalNAc modification during the synthesis process. This approach simplifies the production process and enhances the efficiency of downstream processes. Optimized coupling strategies such as GalNAc alNYLamL96 demonstrate how integrating delivery groups during the synthesis stage can improve targeting and efficacy.

When developing GalNAc-siRNA drugs (especially liver-targeting drugs), the scientific research and industrial communities usually prefer to use PS resins because of their high loading capacity, which is suitable for the synthesis of long-chain siRNAs and meets the requirements for large-scale production. Under the same synthesis column volume, PS resins can provide several times higher drug output than traditional CPG.

However, as oligonucleotide drugs evolve towards longer chains and more complex structures, CPG-type solid-phase carriers have become indispensable for carrying complex modifications (such as cell delivery groups). Poresyn Solutions’ hyper-link CPG solid-phase carrier, with its high loading capacity, high purity, and strong modification compatibility, makes GalNAc coupling more efficient and reliable. This makes it an ideal platform for the next generation of cell delivery integrated oligonucleotide synthesis, bridging the gap between high-yield production and advanced drug design.

Current Popular Cell Delivery Methods for Oligonucleotide Therapeutics

The following table summarizes the most commonly used cell delivery strategies for oligonucleotide therapeutics. It highlights their mechanism of action, the types of oligonucleotides they are typically applied to, and the main advantages and limitations of each approach. This helps researchers and developers choose the most suitable delivery method based on their target cells and therapeutic needs.

Penetrating the cell membrane

Oligonucleotides are essentially nucleic acid fragments, carrying a negative charge. The surface of the cell membrane also carries a negative charge. Due to the principle of like charges repelling each other, the exposed nucleic acids are difficult to approach and penetrate the cell membrane. Nucleic acid molecules are large in size and highly soluble in water, so they cannot enter the cell through simple diffusion; neutralizing the charge or using receptor-mediated endocytosis to forcibly bring the drug into the cell.

Preventing degradation in blood

There are a large number of nucleases (Nucleases) in human blood and tissue fluid. Unmodified or unprotected siRNA typically has a half-life of only a few minutes in the blood. The function of the delivery system: Physically shielding nucleic acid molecules to prevent them from being degraded by enzymes.

Prevent rapid clearance by the kidneys

Oligonucleotides (especially ASOs) can easily be filtered out by the glomeruli and excreted. The delivery system increases the molecular weight of the active molecules or binds to plasma proteins to prolong the residence time of the drug in the circulatory system.

Precise targeting

The delivery system can precisely deliver oligo drugs to the diseased tissues. For example, the GalNAc technology is currently the most successful case. By attaching a “hook” (GalNAc sugar chain) to the nucleic acid, it can precisely recognize the receptors on the surface of liver cells, achieving efficient targeting of the liver. LNP lipid nanoparticles: They can selectively accumulate in specific tissues, such as the lungs, spleen, heart, even tumors, the brain, and bone marrow, through specific regulation of LNP.

Endosomal escape

After oligo drugs enter the cell membrane, they are usually encapsulated in “endosomes”. If they cannot escape from the endosomes and enter the cytoplasm, the drugs will eventually be degraded by lysosomes. This is one of the biggest challenges for oligonucleotide drugs at present. Cell delivery system can be specifically designed with “endosomal escape” function (such as ionizable lipids) can rupture the endosomes when the environmental pH changes, releasing the drugs.

Future Trends in Oligonucleotide Therapeutics

The oligonucleotide industry is at a pivotal inflection point, moving from simple primers to complex, large-molecule medicines. Future progress is defined by three pillars: increased sequence length, sophisticated chemical modifications, and commercial-scale manufacturing efficiency.

Longer and More Complex Sequences: The gRNA Frontier

R&D is shifting from traditional 20nt ASOs to sequences exceeding 60nt to 120nt. These molecules act as the “navigational scalpels” for modern gene editing.

The Industry Giants: Following the landmark approval of Casgevy by CRISPR Therapeutics, the demand for high-purity gRNA has skyrocketed. Intellia Therapeutics and Editas Medicine are pushing in vivo programs that require extreme fidelity to avoid off-target effects.

Next-generation editing takes complexity even further:

• Base & Prime Editing: Companies like Beam Therapeutics and Prime Medicine utilize pegRNA—molecules significantly longer and more complex than standard gRNA, as they must carry both targeting and template information.
• Hybrid Innovations: Caribou Biosciences is pioneering chRDNA (RNA-DNA hybrid guides) to improve precision, creating a unique challenge for traditional solid-phase synthesis platforms.
• Epigenetic Control: Newcomers like Chroma Medicine use gRNA to target the “on/off” switches of genes without altering the DNA sequence, requiring long-chain probes with stable secondary structures.

Novel Chemical Modifications for Targeted Delivery

To ensure stability and reach non-liver tissues (heart, brain, muscle), chemical complexity is evolving beyond standard GalNAc conjugation.

Enhanced Stability: Use of UNA, GNA, and non-natural bases to resist nuclease degradation, as seen in Verve Therapeutics’ cardiovascular programs.

Tissue Specificity: Development of ultra-large, sensitive ligands for extra-hepatic delivery that require inert, high-permeability synthesis supports.

Manufacturing Innovation & Process Optimization

As RNA drugs move toward commercial mass production, the focus has shifted from “lab-scale discovery” to “industrial scalability.”

The PoresynSolutions Impact: Manufacturing innovation is centered on breaking the “Length-vs-Loading” paradox. Our hybrid carrier—combining CPG’s structural stability with Resin’s high loading (3–6x increase)—is the critical catalyst for GMP-scale production of 100nt+ gRNA.

By boosting crude purity from 50% to over 80% at the synthesis stage, manufacturers can drastically simplify downstream HPLC purification. This reduces solvent consumption by tons and significantly lowers the Cost of Goods (COGS), making life-saving gene therapies more accessible to patients worldwide.